I'm photographing couples at a dance and wondering how to best go about model releases so i can use the shots for my online site. do i have to get every person to sign it OR is there something i can write into the contract that one of the board members will sign?

You could just have a table beside you with the paper on it and ask as people wait in line to read the file and sign before they have their portrait taken. You can then either a) assume everyone signs OR b) take note of the image number and write it at the top of their signed model release forms so you know who signed and who didn't.

Photos on a web site fall under the same contexts as other kinds of publishing: editorial, commercial, or artwork. If you put your photos on your own website, this is a case where you are the publisher. However, publicizing photos as being "for sale" does not require a model release so long as you are only selling the photos, not promoting a third party product or service from yourself. Nor can you attribute (or imply) that someone (in a photo) advocates your business, an idea, or anything. You can sell these photos too, although the buyer's use of the photos need to be considered. Again, see Model Release Primer for a detailed discussion.
The point is, photos of people should not appear to express an opinion. If they do, a release is required. An example might be a photo of a woman with the caption, "I'm Jan, and I love to stay at the Jimminy Glick Hotel." This is advocating a company, so it requires a release. If the photo happens to be on the same page as other ads, but clearly not associated with the ads, then no release is required. Ads on web pages are very common, and it's rare that people associate a relationship between the advertiser and the content. However, some people try to push the limits, especially when it comes to political and relgious views.

so just for the point of being able to show them on my web page (not even selling them to others (they will be sold to the client) ) i need no model release? Yes i could have them sign at the table just one more thing though to do at that time.